Total hip joint prosthesis of a type including an acetabular cup implant provided with a ball socket for mounting operationally a femoral ball on a femoral pin are knon in the art.
Some problems have existed in the prior art devices for various reasons.
It is sometimes difficult to obtain an initial and lasting relative positionment of the socket in the implant so that the ball will continue optimally functional in use regardless of positional movement or rotation of the user's leg.
The acetabular cup implant of the present invention, and as also shown in my prior U.S. patents and in devices of others in the art, have included position maintaining means such as spikes or blades or hemispheroidal devices designed to hold the implant firmly in place while resisting rotational, compressive, and distracting forces on the implant during an initial phase of bony ingrowth and subsequent fixation with respect to the bone opening in which placed. Means to relatively fix the components over a long time have additionally included use of a porous surface or coated cup design to facilitate a normal growth of bone into fixation in and with respect to the openings in the porous surface.
In combination, the heretofore used spikes or other fixation means and the porous surface have provided relatively favorable results in use.
Certain drawbacks have existed, however, in prior known devices both as regards the initial positionment of the cup within which the femoral head is rotatably mounted or contained, and initial and lengthy fixation of the acetabular cup with respect to the bone within which implanted devices have not been entirely satisfactory. As pointed out above, certain steps have heretore been utilized to provide a friction fixation for a primary initial fixation and a secondary or continuing arrangement or means wherein the specific outer porous surfaces of the cup intergrows with the bone for a long-range fixation. This broad combination of concepts is known in the art. The present invention, however, provides new and highly improved results in construction and use of the hip prosthesis as distinguished from the prior art and the results obtained provide a most desirable initial and continuing living connection or interconnection between the implant and the bone which is indepedent of any sizing of the porous oversurface.
It will also be noted that the present invention is usable in such a manner that the acetabular cup with the ball socket can be positionally moved subsequent to the initial positionment in a bore provided in the bone so that the implanting position can insure optimum alignment with the femoral ball or head on a femoral pin regardless of position or use of a leg of the user and will prevent a disconnection (or dislocation) between these two portions of a prosthesis.
Also as will be apparent from the following disclosure, the so-adjustable cup implant can be provided with fins which can either be permanent or which can be placeable with respect to the implant following positionment thereof, these fins being longitudinally positioned with respect to the axis of the implant. The total external surface of the implant and/or the longitudinal fixation fins can have a porous or pore arrangement which will provide the desirable initial and continuing living connection between the implant and the bone. It can also be left bare of any porosity and left to remain fitted into its final position by a friction-fit alone, although the bony ingrowth mode of fixation will be the preferred one.
Anchoring elements in various forms are known in the prior art. For instance, in my aforementioned U.S. Pat. Nos. 3,808,606 and 3,840,904, and in U.S. Pat. No. 3,528,199 there are shown anchoring spikes. U.S. Pat. No. 3,641,590 uses drifts or pins. The present device differs from these prior art cups in that the fins, or outriggers, of the present invention extend generally longitudinally rewardly of the body of the cup from the front face, and extend diametrically radially beyond the perimeter of the body at the front face.
While certain forms of the present invention will be specifically shown and described hereinafter, obviously the invention is not limited to the specific structures and variations disclosed but will permit of obvious variations within the scope of the invention as defined by the claims herein.
Other and additional meritorious features and advances in the art will be apparent from the following disclosure.